1. Field of Invention
The present invention relates to a chemical supplying device. More particularly, the present invention relates to a device that automatically renews a chemical and a method for the same.
2. Description of Related Art
Different chemicals in the industry are often used to achieve different industrial objectives. To accommodate different processes and equipment in a factory, all types of automatic chemical supplying devices have been developed to meet the demands for low cost and high throughput.
Conventionally, in the process for preparing chemicals for use in a process, a chemical of appropriate concentration can be prepared in a mixer tank. The chemical prepared in the mixer tank is conveyed to a buffer tank. The chemical in the buffer tank is then supplied to the required machine by pipes.
To achieve the objective of automatic control, a scale is installed below the mixer tank. The scale measures the net weight of the mixer tank and the chemical therein. When a reading obtained by the scale is equal to the net weight of the mixer tank, it means that the chemical in the mixer tank is used up. Here, the mixer tank is automatically supplied with chemical to ensure that the mixer tank contains enough chemicals to adequately supply the buffer tank.
However, a layer of chemical residue may remain on the wall and bottom of the mixer tank after the mixer tank has been used for a long time. In addition, an exhaust for ventilation affects the weight measurement accuracy of the mixer tank. So, even if the chemical in the mixer tank is used up, the reading measured by the scale is still larger than the net weight of the mixer tank. Thus, the mixer tank is not automatically renewed with the chemical. When the buffer tank needs more of the chemical, a control signal is sent to activate a mixer pump, which conveys the chemical from the mixer tank to the buffer tank. Since there is no chemical left in the mixer tank, the mixer tank pump idles. As a result, the process comes to a standstill.